The Second Man on the Moon was on Reddit yesterday doing an AMA. When asked what advice he'd like to give to Space X's Elon Musk, Aldrin's response was decidedly unsympathetic.

Aldrin's appearance on Reddit yesterday was part of a social media campaign to promote the 45th Anniversary of the Apollo 11 moon landing. There's even a new YouTube channel devoted to it. But when asked about space tourists cavorting around Mars, here's was the 84 year-old retired astronaut had to say:

There is very little doubt, in my mind, that what the next monumental achievement of humanity will be the first landing by an Earthling, a human being, on the planet Mars. And I expect that within 2 decades of the 5th anniversary of the first landing on the moon, that within 2 decades America will lead an international presence on Planet Mars.

Some people may be rooting for Elon - I think he could, with his SpaceX, contribute considerably, enormously, to an international activity not only at the moon but also on Mars. I have considered whether a landing on Mars could be done by the private sector. It conflicts with my very strong idea, concept, conviction, that the first human beings to land on Mars should not come back to Earth. They should be the beginning of a build-up of a colony / settlement, I call it a "permanence." A settlement you can visit once or twice, come back, and then decide you want to settle. Same with a colony. But you want it to be permanent from the get-go, from the very first. I know that many people don't feel that that should be done. Some people even consider it distinctly a suicide mission. Not me! Not at all. Because we will plan, we will construct from the moon of Mars, over a period of 6-7 years, the landing of different objects at the landing site that will be brought together to form a complete Mars habitat and laboratory, similar to what has been done at the Moon.

Tourism trips to Mars and back are just not the appropriate way for human beings from Earth - to have an individual company, no matter how smart, send people to mars and bring them back, it is VERY very expensive. It delays the obtaining of permanence, internationally. Your question referred to a monumental achievement by humanity - that should not be one private company at all, it should be a collection of the best from all the countries on Earth, and the leader of the nation or the groups who makes a commitment to do that in 2 decades will be remembered throughout history, hundreds and thousands of years in the future of the history of humanity, beginning, commencing, a human occupation of the solar system.

I'm actually kind of partial to this view. A one-way mission is enormously less complicated than a return trip. What's more, Aldrin is spot-on about the initial wave of colonists setting up the required infrastructure for future colonists — and eventually tourists. At the same time, however, we shouldn't spurn the efforts of the private sector, especially on account of its ability to innovate and inspire competition.